1. Field of the Invention
This invention relates to post-mix beverage dispensers and to post-mix dispensing valves for mixing together and dispensing a controlled ratio of syrup and carbonated water; more particularly, this invention concerns a post-mix dispensing valve including inside of the dispensing valve itself a self-contained, double-acting piston-cylinder volumetric ratio control device with a direct acting electrical solenoid control valve means.
2. Description of the Prior Art
Known post-mix dispensing valves (alternatively known in the art as dispensing heads or faucets) control syrup and soda (carbonated water) flow with two mechanical flow controls that are adjusted independently of each other to achieve proper mixture ratio. If either flow control malfunctions or changes, the ratio will change because one flow control cannot compensate for the variations of the other. The mechanical flow controls, which require high flowing pressures (about 50 psig) to function properly, do not compensate for viscosity changes caused by temperature fluctuations. New electrical flow control valves including sensors and microprocessors are being developed to overcome these problems, however, they are relatively complicated and expensive.
U.S. Pat. No. 2,427,429 to Waite shows a coin operated cup dispenser using a double-acting piston-cylinder unit which is very large and complex and requires a complex and large electrical-hydraulic pilot operating mechanism to turn a rotary valve containing eight ports. Waite has two separate pistons in two separate cylinders and has a relatively large residual storage capacity. U.S. Pat. No. 2,736,466 to Rodth shows a liquid metering and dispensing device that has an electrical-mechanical pilot operating mechanism with a cam actuator which in turn operates four double-acting valves. Rodth's device is not self-contained inside of a post-mix dispensing valve, and his water chamber has a volume that is not emptied at each stroke. Rodth employs check valves in his syrup line; thus, he cannot use a pressurized syrup source because the syrup would just "blow-through" the check valves.